In the past, various processes have been proposed for the manufacture of synthetic polymer fibers by the general technique of combining such polymers with various vaporizable liquids and, at elevated temperature and pressure, passing such mixtures through a nozzle into a zone of lower pressure (i.e. "flashing" such mixture). In such processes, for example those described in U.S. Pat. No. 3,081,519, British Pat. No. 1,262,531 and German Offenlegungsschrift 1,958,609, polymer solutions are formed with various solvents and such solutions are flashed to form fibers. In other processes, such as those described in German Offenlegungsschrift 2,147,461 and U.S. Pat. No. 3,402,231 a molten polymer is dispersed in water, optionally together with a very minor amount of solvent for the polymer and this mixture is flashed to form fibers. In yet another process, such as described in French Pat. No. 1,350,931, a minor amount of water is dispersed in a molten polymer and this mixture is flashed to form fibers.
However, all of the foregoing processes have practical shortcomings with respect to the quality of the fiber which may be produced and they all suffer from various inherent economic disadvantages. In an attempt to overcome these disadvantages, yet other processes have been proposed, such as described in German Offenlegungsschriften 2,121,512 and 2,144,409 and in U.S. Patent Application No. 295,339 filed Oct. 5, 1972, commonly assigned with the present application, in which an emulsion of a polymer solution in water is flashed to form fibers. While such processes are capable of producing improved fiber in comparison with the previously mentioned processes, the fiber produced still has limited strength properties and it is therefore desirable to provide improved processes which are capable of producing fiber with superior strength and other properties.